In a Tuesday CNN interview, Trump's former presidential rival stood by his criticisms of the mogul. But he maintained that the presumptive Republican presidential nominee was a positive alternative to Democratic presidential frontrunner Hillary Clinton.

"I'm not going to sit here right now and become his chief critic over the next six months, because he deserves the opportunity to go forward and make his argument and try to win," Rubio said.

Indeed, Rubio is far from the only candidate to awkwardly reverse course on negative statements about the inflammatory presidential candidate. Former Trump rivals such as Sen. Rand Paul, former Louisiana Gov. Bobby Jindal, and former Texas Gov. Rick Perry, among others, have found themselves walking back strongly worded criticisms of Trump.

Here are 9 prominent Republican politicians who have reversed course on Trump:

1/

Former Louisiana Gov. Bobby Jindal

Stephen Maturen/Getty Images

In a September op-ed for CNN, then Republican presidential candidate Jindal described Trump as "a shallow, unserious, substance-free, narcissistic egomaniac."

"We can decide to win, or we can be the biggest fools in history and put our faith not in our principles, but in an egomaniac who has no principles," Jindal wrote.

But following Trump's victory in the Republican presidential primary, Jindal offered a very tepid endorsement of the real-estate magnate.

"I think electing Donald Trump would be the second-worst thing we could do this November, better only than electing Hillary Clinton to serve as the third term for the Obama administration's radical policies," Jindal wrote in The Wall Street Journal.

2/

Former Texas Gov. Rick Perry

Michael B. Thomas/Getty Images

During his short-lived 2016 presidential bid, Perry called Trump a "cancer on conservatism" and criticized his inflammatory rhetoric about Mexican immigrants.

"Demeaning people of Hispanic heritage is not just ignorant. It betrays the example of Christ," Perry said in his September concession speech. "We can enforce our laws and our borders, and we can love all who live within our borders, without betraying our values."

But after Sen. Ted Cruz dropped out of the race last week, Perry quickly endorsed the presumptive nominee.

"He is not a perfect man," Perry told CNN. "But what I do believe is that he loves this country and he will surround himself with capable, experienced people and he will listen to them."

3/

Sen. Rand Paul

REUTERS/Scott Morgan

Last month, Paul said he would support Trump in a likely matchup between Democratic presidential frontrunner Hillary Clinton.

New Jersey Gov. Chris Christie

Christie became the first major former presidential candidate to endorse Trump. But just a few months earlier, he was warning voters about Trump's preparedness for the office.

"We do not need reality TV in the Oval Office right now," Christie said in December. "President of the United States is not a place for an entertainer."

7/

Wisconsin Gov. Scott Walker

AP Photo/Paul Sancya

When Walker dropped out of the presidential race after just three months, the governor called on many of his Republican presidential rivals to do the same in order to consolidate support around a conservative candidate.

"It has drifted into personal attacks. In the end, I believe that the voters want to be for something and not against someone," Walker said in his concession speech. "Instead of talking about how bad things are, we want to hear how we can make them better for everyone."

Yet late last month, Walker signaled he'd support the GOP nominee against Clinton — though he refused to say Trump's name.

8/

Sen. Tim Scott

AP Photo/Jacquelyn Martin

Scott, a former Rubio endorser, said last week that he would support the Republican presidential nominee.

Though Scott was not a particularly vocal critic of the real-estate magnate, he did condemn Trump's initial refusal to denounce an endorsement from the former leader of the Ku Klux Klan.

"Any candidate who cannot immediately condemn a hate group like the KKK does not represent the Republican Party, and will not unite it," Scott wrote in a statement. "If Donald Trump can't take a stand against the KKK, we cannot trust him to stand up for America against Putin, Iran, or ISIS."